Because LCD devices have the advantages of portability, low power consumption, and low radiation, they have been widely used in various portable information products such as notebooks, personal digital assistants (PDAs), video cameras, and the like. Furthermore, LCD devices are considered by many to have the potential to completely replace CRT (cathode ray tube) monitors and televisions.
FIG. 7 is an abbreviated diagram of a typical driving circuit for an LCD panel. The driving circuit 10 includes a plurality of parallel gate lines 101, a plurality of parallel data lines 102 orthogonal to and isolated from the gate lines 101, a plurality of thin film transistors 103 positioned near crossings of corresponding gate lines 101 and corresponding data lines 102, a plurality of gate driving circuits 110 for driving the gate lines 101, and a plurality of data driving circuits 120 for driving the data lines 102.
Also referring to FIG. 8, two adjacent gate lines 101 (Gn, Gn-1) and two adjacent data lines 102 (Dm-1, Dm) cooperatively define a pixel region (not labeled). In each pixel region, the driving circuit 10 further includes a pixel electrode 104 and a common electrode 105. The pixel electrode 104 and the common electrode 105 cooperatively form a storage capacitor 106. The thin film transistor 103 includes a gate electrode 1031 connected to a corresponding gate line Gn-1, a source electrode 1032 connected to a corresponding data line Dm-1, and a drain electrode 1033 connected to the pixel electrode 104.
Due to the resistance R of the gate lines 101 and the parasitic capacitance Cgd generated between the gate electrode 1031 and the drain electrode 1033 of the thin film transistor 103, a resistance-capacitance (RC) delay circuit is generated in the pixel region. The RC delay circuit is liable to distort the scanning signals applied to the gate lines 101. The degree of distortion is determined by the resistance R of the gate lines 101 and the parasitic capacitance Cgd.
FIG. 9 shows a waveform diagram of two driving voltages respectively applied to two pixel regions coupled to the same gate line 101, wherein one of the pixel regions is nearest to the corresponding gate driving circuit 110, and the other pixel region is farthest from the same corresponding gate driving circuit 110. Voff represents a shutting off voltage of the thin film transistors 103 in the two pixel regions, Vg1 and Vg2 respectively represent scanning signals applied to the pixel regions nearest to and farthest from the gate driving circuit 110, and Vd1 and Vd2 respectively represent data voltage signals applied to the pixel regions nearest to and farthest from the gate driving circuit 110.
The date voltage signals Vd1 and Vd2 are reversed at time t0. That is, at the time t0, the thin film transistors 103 in the pixel regions of the first row should be shut off, and the thin film transistors 103 in the pixel regions of the second row should be opened. However, the thin film transistors 103 generate distortion due to the scanning signals Vg1 and Vg2, and shut off at time t1 and time t2 respectively. Therefore the reversed data signals Vd1 and Vd2 are respectively transmitted into the storage capacitors 106 of the pixel regions during a time period from t0 to t1 and a time period from t0 to t2 respectively. This makes the storage capacitors 106 undergo rapid electrical leakages during the periods from t0 to t1 and from t0 to t2 respectively.
In each row of the pixel regions, the storage capacitors 106 that are nearest to the gate driving circuit 110 are liable to undergo rapid electrical leakages during the period from t0 to t1. In each row of the pixel regions, the storage capacitors 106 that are farthest from the gate driving circuit 110 are liable to undergo rapid electrical leakages during the period from t0 to t2.
In general, the period from to t1 is very short, and can be ignored. However, the period from t0 to t2 is relatively long, and significant electrical leakages can occur during this time. This prevents the LCD panel from displaying high quality black images.
Accordingly, what is needed is a driving circuit that can overcome the above-described deficiencies. What is also needed is an LCD panel utilizing such driving circuit.